Preference testing procedures involving both restricted and unrestricted access to two solutions will be used to evaluate the effect of a rat's prior experience with either water, saline, sucrose or saccharin solution on its subsequent preference for that fluid when thirsty. Rat pups will be reared on a specific solution, repeatedly deprived and hydrated with it as an adult and then given a choice between it and an alternative fluid in both resticted and unrestricted preference tests. These experiments will provide the basis for follow- up studies that will isolate the effects of early rearing experience with a particular fluid from the effects of correlating a particular fluid with recovery from dehydration on subsequent fluid preference.